The SWREV field in OTP-eFuses is used to implement software rollback protection, preventing attackers from downgrading the primary application firmware to older versions with known vulnerabilities. When a device boots, TIFS/BOOT ROM code compares the software revision value embedded in the boot image certificate against the SWREV value programmed into the OTP-eFuses. If the certificate's software revision is less than the OTP SWREV value, the boot process is rejected, ensuring authentication and loading of equal or higher SWREV revision numbers.

Components for which SWREV can be updated are:

1. Software Revision SBL.
2. Software Revision SYSFW/TIFS.
3. Software Revision Secure Board Configuration.

Update Procedure:

• HS-SE TIFS provides the capability to update SWREV values at runtime using the TISCI_MSG_WRITE_SWREV command.
• VPP_MCU is required for eFuse write operations.